PV module temp [RE-wrenches]

[Bill Brooks]

Joel,

Careful with your units. The boys on the other side of the globe might get a
little testy. You are referring to 20C hotter than ambient temp (probably
more than that for roof mounted arrays) which is only 36F hotter than
ambient (not 68F--68F=20C when we are talking actual temperatures, not
temperature difference). Degrees C is 1.8 times degrees F when looking at
differences.

On a 40C day in full sun (1000 W/m2), I measured 70C (158F) on an open rack
array. That's 30C which is worst case rather than 20C which might be an
annual average.

Bill.


> -----Original Message-----
> From: Joel Davidson [mailto:joeldavidson at earthlink.net]
> Sent: Tuesday, September 25, 2001 2:53 PM
> To: RE-wrenches at topica.com
> Subject: Re: PV module temp [RE-wrenches]
>
>
> Single crystal and polycrystalline cell temperature is approx. 20
> degrees C. (68 F.)
> above ambient air temperature. The sensor should measure the cell
> temperature, not
> the atmosphere at the back of the panel.
>
> Smitty wrote:
>
> > Trav, the insulation is probably giving you a high reading. The
> sensor should be
> > exposed to the same atmosphere that the back of the panel is. Smitty.
> >
> > "Travis Creswell, Ozark Solar" wrote:
> >
> > > Hey Gang,
> > >
> > > I have hooked up a Heliotrope Quadra Temp four channel temp
> monitor that
> > > uses 10k sensors.  One of the channels is monitoring temp on
> the back of a
> > > module in my roof mounted PV array.  I'm seeing temps of
> nearly 140 F on
> > > sunny days that the ambient temp doesn't get past 80 F.  That
> seems pretty
> > > high.  The sensor is fine as it reads ambient temp accurately
> after sunset
> > > plus I checked it before I installed it.  I siliconed the
> sensor along with
> > > a small piece of Armaflex insulation on the back
> approximately in the center
> > > of the module.
> > >
> > > I insulated it so the temp would be more accurate but now I
> am wondering if
> > > I'm not holding heat in with the insulation causing the temp
> to be too high?
> > >  But if I don't insulate it won't it read too cool?
> > >
> > > Suggestions?
> > >
> > > Thanks in advance.
> > >
> > > Travis Creswell
> > > Ozark Solar
> > >
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